"Temperatures in the Antarctic Peninsula started rising naturally 600 years ago, long before man-made climate changes further increased them, scientists said in a study on Wednesday that helps explain the recent collapses of vast ice shelves."

"The study, reconstructing ancient temperatures to understand a region that is warming faster than anywhere else in the southern hemisphere, said a current warming rate of 2.6 degrees Celsius (4.7 Fahrenheit) per century was "unusual" but not unprecedented.

"By the time the unusual recent warming began, the Antarctic Peninsula ice shelves were already poised for the dramatic break-ups observed from the 1990s onwards," said the British Antarctic Survey, which led the study published in the journal Nature.

A warming trend caused by natural variations, perhaps affecting winds and ocean currents, began 600 years ago and made ice shelves - tracts of ice floating on the ocean around the peninsula - vulnerable to even faster warming since 1920."